1" PEX or 1" PVC when hooking up new softener?

All the current connections and piping in my well house are 1" PVC. The softener and Filox filter are both 1" pipe connections. I have been told by numerous people to use PEX instead of PVC. I have the pex tool and I have done plumbing with both. Its just that the ID of the pex is quite a bit smaller than PVC. Does it matter??